1. Technical Field
The present invention relates to a method for manufacturing copper-based nanoparticles, more particularly, to a method for manufacturing copper-based nanoparticles whose oxidation number and size can be controlled and which can be produced in mass.
2. Description of the Related Art
In response to demands for electronic components with miniaturization and high-densification, needs for metal patterning in a thin film using inkjet or formation of microwiring on a substrate have been increased. To implement this, it is necessary to produce conductive ink which is made from nano size of copper particles having a uniform shape, a narrow distribution of particles and an excellent dispersibility.
There are various methods of producing copper nanoparticles, such as mechanical grinding method, co-precipitation method, spray, sol-gel method, electro-deposition method, and microemulsion method, etc. In case of producing metal nanoparticles by the co-precipitation method widely used, it is impossible to control size, shape, size distribution of particles. In case of producing by the electro-deposition method and sol-gel method, it is difficult to produce in mass production and production cost is high. Also, in case of producing by the microemulsion method, it is easy to control size, shape, size distribution of particles, however, it is not suitable for practical use as the production process is complicated.
Recently, a copper nanoparticle synthetic method using solution synthesis has been suggested. Conventional nanoparticle synthetic methods using solution synthesis are, for example, thermal decomposition method and reduction method. In case of thermal decomposition method of Cu nanoparticles requires high cost since it uses expensive precursor such as [Cu(u-mesitil)5] or Cu(acac)2.
As methods of preparing copper nanoparticles with the size less than several tens of nm, TDMA (thermal decomposition of metal acetate) suggested by O'Brein et al. has been well-known. This method is a thermal decomposition of metal acetates such as Mn(CH3CO2)2, Cu(CH3CO2) in an oleic acid, in which the oleic acid functions as a solvent and a capping molecule. In case of copper nanoparticles, the example using trioctylamine simultaneously was published in J. Am. Chem. Soc. 2005. Also, Hyeon group published that copper particle synthesis using the thermal decomposition of copper acetyloacetate (Cu(acac)2) in oleylamine. These methods are examples that use the high temperature thermal decomposition in solution.
Recently, methods for manufacturing copper nanoparticles using the thermal decomposition have been reported after designing a copper precursor using the CVD precursor design technique (KR Patent No. 10-2005-35606). It has an advantage that copper nanoparticles can be synthesized by the thermal decomposition at a low temperature of less than 200° C. It, however, requires a new precursor design and high manufacturing costs.
Also, to synthesize copper nanoparticles using reduction method, a reducing agent is added using micelle method. However, in case of the micelle method, the concentration of an available copper precursor is low, thus synthesis with high concentration cannot be achieved. Also, homogenous nucleation is impossible as the reducing agent is added and productivity is low as growth rate cannot be controlled.
The above methods have problems that the reaction cannot be processed uniformly in case of using more than a certain amount, since thermal decomposition is rapidly performed by injecting a certain amount of all precursors at the same time which are used in the synthesis, or metal nitride or metal salt which are used in the synthesis are reduced using an organic reducing agent.
Therefore, a method for manufacturing copper nanoparticles having high concentration and uniform size is demanded.